Suction Device

ABSTRACT

This invention relates to plunger operated liquid dispensers, such as hand held pipettors, which are used to portion liquids. Specifically the invention relates to a reliable removal of a liquid from the liquid dispenser. According to the invention the plunger of the liquid dispenser is arranged into a speeded up movement while removing the liquid. This change in speed is preferably sudden.

This invention relates to plunger operated liquid dispensers, such asmanual pipettors, which are used to dispense liquids. Specifically theinvention relates to reliable removal of a liquid from the liquiddispenser. Especially preferable the invention is in such liquiddispensers, which are used to handle relatively small sample amounts,such as around one microliter. More specifically the object of theinvention is what is said in the preambles of the independent claims.

Plunger operated liquid dispensers normally have a function which iscalled a blow-out. Therein the movement of the plunger while removing aliquid (secondary movement) is longer than the movement which has beenmade by the plunger while receiving the liquid. Thus removal of theliquid can be improved when compared to the situation when the plungerwould move the same distance in both the receiving and removal phases.In manual pipettors this function is usually accomplished by twosprings, whereas in electronic pipettors this function is possible toaccomplish simply by continuing the movement of the plunger with thehelp of a motor. In both approaches only one plunger is used.

Above mentioned removing problem emphasizes with small volumes when thediameter of the plunger is small in relation to the removal opening ofthe tip. What usually happens is that the liquid is not removed from thetip but it revolves to the outer surface of the tip. Then the liquiddrop must be mechanically removed by the user by transferring the liquidmechanically to a wall of the tube which is receiving the sample.Usually the out pipetting is repeated several times. Another solution isto saturate the sample to a liquid already existing in the tube. In theend it is always up to carefulness of the person performing thepipetting how well the liquid actually tranfers and how much stillremains in the tip. Naturally these kind of different contacts alsoresults in that different contamination risks increase.

More generally the weakness in pipettors can be said to be thisdifficult pipetting of small portion volumes. The volumes below 10 μl donot come off from the pipettor tip, whereat they must be pipettedsaturated in a liquid or they must be able to make that catch in thewall of a test tube. This has resulted in that manual pipettors are usedwhen small volumes are pipetted because manual pipettors enable severalremovals successively. However, the accuracy is then quite poor.

The international standards allow large CV percents for 0.1-2 μlvolumes. However, smaller volumes usually are portion volumes of a testsample which determine the accuracy of the whole test. These standardsare clearly drafted taking into consideration the problem caused by thesmall plunger diameter.

In automatic dispensers which require that different tip must be usedfor each sample can not dispense small volumes, which results in that alot of reagences must be used. In addition if a sample is tried to makea catch to the bottom of a test tube/plate with these automaticdispensers the accuracy of the structure of this kind of device must becontrolled extremely well, and in the worst case the situation is suchthat a bad accuracy appears occasionally.

In turn, in hand held pipettors, especially in 10 μl pipettors, theproblem is different attachment of the tips, because of that the catchof a sample to a test plate is extremely difficult.

One approach is to use two nested plungers. The inner plunger is aportioning plunger whose movement distance defines the volume to bedispensed. The movement of this portioning plunger is the same whilereceiving the liquid and while removing it. The outer plunger is ablow-out plunger, which starts it's movement only after the portioningplunger has carried out it's removal movement.

Another approach is to use two plungers so that these two plungers actsimultaneously during the removal, then more pressure is developed to atip of the pipettor. Even the smallest drops which tend the remain inthe tip are aspired to be removed from the tip.

Based on what is said above now has been noticed that the removingproblems of the liquid relate to the slow movement of the plunger duringthe removal phase. The purpose of this invention is thus to developfurther the function of the pipettors in situations where a tip of theliquid dispenser is aspired to be emptied so that there is no need forcontact with a test tube or with a liquid, and that dividing of theliquid between the tube and the tip remains the same betweenportionings.

The teaching of the present invention in relation to the beforementioned state of the art is that the movement of the plunger of theliquid dispenser is fastened during removal of the liquid.

This change in speed is preferably sudden, when the sample is as it werelaunched out from the liquid dispenser. More specifically the inventionis characterized in that what is said in the characterizing parts of theindependent claims. Some preferable embodiments are presented in thedependent claims.

Thought behind the invention is that the sample is portioned with oneplunger in a way that the plunger is a small diameter plunger in areceiving phase and a large diameter plunger in a removal phase. Theseemingly larger diameter of the plunger is provided with a multiplemovement speed. The movement speed can be used in the most preferablephase to optimize portioning. The high movement speed and it'sactivation can be accomplished with several technical components.

Electrical hand held pipettors are known to have such adjustmentpossibilities that the movement of the plunger can be adjusted usingprograms. This intrinsically is obvious for a person skilled in the artthrough experimentation so that an optimal movement speed can beachieved for the plunger. These previously known electrical pipettorshowever do not make difference between the receiving and removal phasesso that the removal movement speed would be fastened to solve thisparticular problem that especially with small volumes during the removalphase the sample tends to revolve to the outer surface of the tip. Alsothe previously known motors do not present such motors which couldproduce sufficient speeds.

Previously mentioned optimatization of the movement speed of the plungeris a substantial part of the present invention. It is important that thereceiving suction is carried out slowly and the removal movement iscarried out with high speed. After what is said here it is obvious for aperson skilled in the art that the mentioned removal movement speed canbe achieved with several different ways. According to the invention theliquid dispenser comprises such means which enable the removal movementof the plunger to be increased very high. With the help of such a fastremoval speed the liquid dispenser tip always empties similarly, whenthe CV percent is comparable also with small volumes.

According to one embodiment of the invention the previously mentionedmeans comprise spring like means, energy means, which produces theenergy needed by the removal movement. Here it must be noted that thespring like means is very preferable but such energy can also beproduced also in a different way, for example in case of an electricalpipettor by programming. Preferably such spring like means can be forexample a spring, or for example a combination utilizing magneticforces. According to this embodiment the spring like means must beactivated, after which activation this activation must be locked withsuitable means. Such activation can be implemented, again as an example,using magnetic forces. Naturally this embodiment also requires meanswhich can release the said activation. Such release means can be forexample a mechanical trigger which may utilize the possible magneticforces.

According to one preferable embodiment the liquid dispenser is anelectronical pipettor, such as for example a Biohit eLine-seriespipettor. A pipettor comprises a cylinder part which is adapted inside abody, inside which cylinder part a plunger moves to dispense liquid. Theplunger has a normal relatively slow movement speed produced by themotor. To implement the invention the pipettor is equipped with launchmeans. These launch means comprise an actuator shaft, which ispreferably made of magnetic steel. In addition the launch means comprisea spring, a magnet and activation means, which is preferably anactivation pin, or similarly functioning mechanical response. To carryout the invention the shaft gets into contact with the magnet. Then thelaunch spring is activated. After this the sample is received normallyby moving the plunger upwards. When the required liquid volume has beenreceived, the plunger stops. When the liquid needs to be removed fromthe sample space, the motor starts again an upward movement. When themovement continues upwards the launch pin comes into contact with aresponse which is preferably provided in the pipettor body. When themovement continues upwards, the launch pin forces the actuator shaftapart from the magnet, whereat the spring forces the actuator in a fastdownward movement, resulting in that the actual suction plunger causesfast movement of the liquid from the sample space when moving downwards,and whereat the liquid does not revolve to the outer wall of the tip butis entirely removed from the tip, which is for example a detachabledisposable tip.

Another embodiment is a hand held mechanical pipettor where the presentinvention is utilized. In a mechanical pipettor the activation of anenergy means can be carried out for example similarly as described aboveduring a downward movement of a plunger, which movement can be forexample a blow-out movement. After this the sample is received normally.Finally the energy means is launched with appropriate means. Suchappropriate means can be for example a trigger provided in the pipettorbody.

In the following reference is made to the attached drawings where ispresented one way for implementing the invention. In the drawings:

FIG. 1 depicts a simplified cross section drawing of a hand heldpipettor;

FIG. 2 depicts slightly more details of the pipettor of FIG. 1; and

FIG. 3 presents pictures a-d which depicts pipettor of FIG. 2 in action.

Similar numbering is used throughout the figures for the parts which areincluded in several figures. Pipettor 10 comprises an inner actuatorshaft 1, a spring 2, a magnet 3, a launch pin 4, an upper response 5, asuction plunger 6, a function plunger 7, a cylinder 8, a motor 9, adisposable tip 11 and a launch means body 12.

The actual actuator implementing the present invention comprises inthese figures the actuator shaft, the magnet and the launch pin.

The suction plunger is connected to the actuator shaft, which isconnected to the function plunger by the magnet. When the motor movesthe function shaft upwards these three (1, 6, 7) move together and thesuction shaft moves inside the cylinder causing the suction function forreceiving a sample to the tip. The spring is arranged between theresponse in the actuator shaft and the launch means body. The magnet issolidly inside the launch means body, and the actuator shaft is arrangedto move inside the launch means body. The launch pin is arranged so thatwhen it comes into contact with the upper response arranged in thepipettor body, it forces the actuator shaft apart from the magnet insidethe launch means body.

The object of the invention is that the volume to be portioned islaunched out with high speed. When implementing the structure it isimportant that the home of the suction plunger is located so that thesuction movement fits before the launch point. This home is especiallypresented in FIG. 3 a. Then according to the invention the sample isreceived in the tip, which position is presented in FIG. 3 b. After thisthe motor is driven slightly more upwards whereat the launch pincontacts the upper response and pushes the actuator shaft apart from themagnet. The contact between the launch pin and the upper response isalso presented in FIG. 3 b. When the actuator shaft has aparted from themagnet, the spring forces the plunger to shoot downwards with high speedas is presented in FIG. 3 c. In hand held electronic pipettors removalof the tip can be preferably carried out during the activation of theactuator for a new suction function. Such activation of the actuator ispresented in FIG. 3 d, where the motor pushes the launch means body withthe help of the function plunger downwards and thus the magnet is againin contact with the actuator shaft.

1. Liquid dispenser, which comprises: a body part, a cylinder partarranged inside the body part; a plunger movably arranged inside thecylinder part; means for moving the plunger; characterized in that theliquid dispenser further comprises: a secondary means for causing aspeeded up emptying movement of the plunger.
 2. Liquid dispenseraccording to claim 1, wherein the secondary means comprises: an energymeans, which provides the energy needed by the emptying movement; alocking means, which locks the activation of said energy means; a launchmeans, which releases the said activation of the said energy means. 3.Liquid dispenser according to claim 2, wherein: the energy means is aspring; the locking means is a magnet; and the launch means is amechanical response.
 4. Liquid dispenser according to claim 3, whereinthe launching means further comprises: an actuator shaft with magneticcharacters, which has a lower part and an upper part, and which actuatorshaft is from it's lower part attached to the suction plunger arrangedat the lower part of the body of the liquid dispenser, and from it'supper part in connection to the magnet, which magnet is connected fromit's other end the a function plunger directed to the upper part of thebody of the liquid dispenser; a launch means body, inside of which theupper part of the actuator shaft extends, and where the magnet isarranged; a combination, where the spring is arranged to be strainedbetween the launch means body and the actuator shaft; a mechanicalresponse, launch pin, arranged in the launch means body, which is fromit's upper part able to be in contact with a response arranged in thebody of the liquid dispenser; a function, wherein when the said contactoccurs the upward movement in relation to the body of the liquiddispenser is continuable, whereat when continuing the movement thelaunch pin is arranged to force the actuator shaft apart from themagnet, whereat the spring is arranged to force the actuator shaft intoa downward movement.
 5. Liquid dispenser according to claim 1, whereinthe liquid dispenser is an electronic dispenser.
 6. Liquid dispenseraccording to claim 1, wherein the liquid dispenser is a multi channeldispenser.
 7. Liquid dispenser according to claim 1, wherein the liquiddispenser is a hand held pipettor.
 8. Method for pipetting a sample witha liquid dispenser, comprising the steps of: receiving the sample to atip of the liquid dispenser; removing the sample from the tip of theliquid dispenser; characterized in that the removal movement forremoving the sample from the tip is performed faster than the suctionmovement.
 9. Method according to claim 8, wherein the liquid dispensercomprises a body, a cylinder part arranged inside the body, a plungermovably arranged inside the cylinder part, means for moving the plunger,and secondary means for moving the plunger and to achieve a speeded upmovement of the plunger, which method further comprises: activating thesecondary means which move the plunger; receiving the sample; andreleasing the secondary means which move the plunger to accomplish thesecondary movement of the plunger.
 10. Method according to claim 9,wherein further the following steps are performed: catching the actuatorshaft with the magnet; and releasing the magnet from the actuator shaft.11. Method according to claim 10, wherein: when the magnet is inconnection with the actuator shaft, the launching means are movedupwards when receiving the sample; when removing the sample themechanical response gets into contact with a response arranged in thebody of the liquid dispenser; continuing the upward movement of thelaunching means until the actuator shaft releases from the magnet;forcing with a spring the actuator shaft released from the magnet into aspeeded up downward movement for an efficient removal of the sample fromthe liquid dispenser.